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      <div><h1>alphaBlend method</h1></div>

    <section class="multi-line-signature">
      <span class="returntype"><a href="dart-ui/Color-class.html">Color</a></span>
            <span class="name ">alphaBlend</span>
(<wbr><span class="parameter" id="alphaBlend-param-foreground"><span class="type-annotation"><a href="dart-ui/Color-class.html">Color</a></span> <span class="parameter-name">foreground</span>, </span> <span class="parameter" id="alphaBlend-param-background"><span class="type-annotation"><a href="dart-ui/Color-class.html">Color</a></span> <span class="parameter-name">background</span></span>)
      
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    <section class="desc markdown">
      <p>Combine the foreground color as a transparent color over top
of a background color, and return the resulting combined color.</p>
<p>This uses standard alpha blending ("SRC over DST") rules to produce a
blended color from two colors. This can be used as a performance
enhancement when trying to avoid needless alpha blending compositing
operations for two things that are solid colors with the same shape, but
overlay each other: instead, just paint one with the combined color.</p>
    </section>
    
    <section class="summary source-code" id="source">
      <h2><span>Implementation</span></h2>
      <pre class="language-dart"><code class="language-dart">static Color alphaBlend(Color foreground, Color background) {
  final int alpha = foreground.alpha;
  if (alpha == 0x00) { &#47;&#47; Foreground completely transparent.
    return background;
  }
  final int invAlpha = 0xff - alpha;
  int backAlpha = background.alpha;
  if (backAlpha == 0xff) { &#47;&#47; Opaque background case
    return new Color.fromARGB(
      0xff,
      (alpha * foreground.red + invAlpha * background.red) ~&#47; 0xff,
      (alpha * foreground.green + invAlpha * background.green) ~&#47; 0xff,
      (alpha * foreground.blue + invAlpha * background.blue) ~&#47; 0xff,
    );
  } else { &#47;&#47; General case
    backAlpha = (backAlpha * invAlpha) ~&#47; 0xff;
    final int outAlpha = alpha + backAlpha;
    assert(outAlpha != 0x00);
    return new Color.fromARGB(
      outAlpha,
      (foreground.red * alpha + background.red * backAlpha) ~&#47; outAlpha,
      (foreground.green * alpha + background.green * backAlpha) ~&#47; outAlpha,
      (foreground.blue * alpha + background.blue * backAlpha) ~&#47; outAlpha,
    );
  }
}</code></pre>
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